Ichinose, Haru

Haru is shown to be a bright and cheerful girl of the Black Class. She aims to become friends with everyone, and is essentially the class's moodmaker. She is kind to everyone without fail until they become hostile with her. Haru is the target that everyone in the class is after.

[Spoiler] Haru's body is revealed to be covered in scars. Hashiri Nio tells Sagae Haruki that Haru has also had a history of killing, despite being the target and her happy personality. Haru has supposedly killed off her brothers. Nio tells the entire group that killing Haru will be difficult because she will use whatever means necessary to survive.

Later, Haru reveals to Tokaku that her life has been at stake for the longest time, and that she has even developed some sort of immunity to sleeping pills (to an extent) after Inukai Isuke tried to drug her. [/Spoiler]